how many calories should you eat

Take your ideal weight and multiply it by 30. This should be the amount of calories you can eat a day. Of course this is not very precise because it doesn’t take important factors like lifestyle and gender into account.
Factors that influence how many calories you should eat:

• Male/female
• Active/sedentary life style
• Age
• Height
• Weight

The US Department of Health and Human Services recommend the following numbers:
Sedentary lifestyle (less than 30 minutes of moderate physical activity/day)

• Male 18-30 yo: 2400 calories
• Female 18-30: 2000 calories
• Male 31-50: 2200 calories
• Female 31-50:  1800 calories
• Male 50+: 2000 calories
• Female 50+: 1600 calories

More active lifestyle (more than 30 minutes of moderate physical activity/day)

• Male 18-30 yo: 2600-3000 calories
• Female 18-30: 2000-2400 calories
• Male 31-50: 2400-3000 calories
• Female 31-50:  2000-2200 calories
• Male 50+: 1800-2200 calories
• Female 50+: 2200-2800 calories

These numbers will maintain your current weight.
To lose weight you should increase your physical activity and reduce your caloric intake.  Try to eat 400 calories less than you are used to and you will soon start losing weight seriously.